History

VR started a modernization project in the early fifties. VR had a small amount of diesel and gasoline-powered railcars since the 1920's, but in 1952 VR had only steam locomotives.

Modern aluminum-carriage diesel powered express multiple units (Dm3 and Dm4) were introduced in 1952.
Related to these orders, VR ordered in 1952 five passenger train diesel locomotives with hydraulic transmission from Valmet

Valmet

' was a Finnish state-owned conglomerate. Valmet was formed in 1951, when the state of Finland decided to group their various factories working on war reparations to the Soviet Union under one company...

Oy, Tampere. The locomotives were delivered in 1955.

Technology

The locomotives had originally two six-cylinder Maybach MD320 diesel engines driving each their own Maybach Mekydro K64B hydraulic-mechanical gearbox. The engines and transmission were placed in the bogies. The engine-transmission units proved to be very unreliable, and in 1956-58 a complete overhaul was done. Among other improvements, the engines were fitted with turbochargers, which increased the power from 450 hp to 600 hp, but simultaneously lowered the RPM from 1700 to 1500 r/min. The new engine designation was Maybach MD325. The gearboxes were changed to another type, Mekydro KL64. After the upgrade, the engines were reasonably reliable, but the reliability of the Maybach Mekydros didn't improve significantly.

Operation

The locomotives carried a gray livery, with wine-red broad stripes around. The gray color and sleek looks earned it the nickname "Lentävä susi" (Flying Wolf).
They pulled mainly passenger trains between Tampere, Helsinki and Turku.
All units were abandoned in 1972.